How to Replace SQL's ISNULL Function with LINQ?

LINQ Equivalent of SQL's ISNULL Function

Question:

How can you emulate the behavior of SQL's ISNULL function in a LINQ query? Consider a join query involving a non-nullable column (xx.Online of type bit) that can contain null values.

Answer:

To handle nullable values in LINQ, you can use the conditional operator (? :) to specify a default value if the aa object is null. The following code demonstrates this:

select new {
    AssetID = x.AssetID,
    Status = aa == null ? (bool?)null : aa.Online; // a Nullable<bool>
}

If you want to set the default to false (rather than null) when aa is null, you can use this code:

select new {
    AssetID = x.AssetID,
    Status = aa == null ? false : aa.Online;
}

Additional Investigation:

It's important to note that using the conditional operator with null values for non-nullable types requires explicit handling. In the provided example, you're returning a Nullable in the first code block, which allows for both null and false values. In contrast, the second code block returns a bool, so null must be explicitly assigned to false if aa is null.

How ISNULL Compares to the Null Coalescing Operator:

The null coalescing operator (??) cannot be used directly to replace ISNULL. The ?? operator only returns a non-null value if both operands are non-null. Therefore, it's not suitable for handling situations where one operand might be null.

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